JPH0241022B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a selenium-tellurium alloy material for an electrophotographic photoreceptor, and an electrophotographic photoreceptor comprising a vapor-deposited photosensitive layer prepared by vacuum-depositing the material. In particular, it is characterized by the addition of more than 100 ppm and less than 1000 ppm of oxygen. By adding oxygen, the residual potential can be reduced while maintaining good dark decay characteristics.

Background of the Invention Electrophotography is a photographic method that utilizes the photoconductivity of substances and electrostatic phenomena, and several methods have been established. The method of obtaining electrophotography through transfer is called the Xerox method.
The Xerox method, as is well known, consists of the following steps: (a) Charging: The surface of a photoreceptor, in which amorphous selenium or selenium alloy with high dark resistance is deposited on a metal substrate, is charged.

(b) Exposure (printing): When exposed to a light image, the electrical resistance of the selenium or selenium alloy in the irradiated area decreases, the surface charge escapes to the metal substrate, and the remaining charge density on the photosensitive plate decreases due to exposure. A difference occurs depending on the amount, and an electrostatic latent image with the same shape as the original image is formed on the surface of the photosensitive plate.

(c) Development: By sprinkling the surface of the photosensitive plate with a mixed powder of toner consisting of fine carbon powder coated with resin and carrier consisting of glass beads, the toner adheres to the latent image area, and the latent image becomes a visible image. Become.

(d) Transfer: When a suitable paper is placed on the surface of the photosensitive plate after development and a corona discharge is applied from the back side, the toner on the photosensitive plate is attracted to the paper and the toner powder image is transferred to the paper.

(e) Fixing: Once the transfer is complete, remove the paper and heat it with an infrared heater to fuse the toner resin to the paper.

By carrying out the above process, a copied image (electrophotography) of the original image can be obtained, but the characteristics such as sharpness and reproducibility of the copied image largely depend on the performance of the photoreceptor selenium or selenium alloy. Although several selenium alloys have been considered, selenium-tellurium alloys are widely used for the purpose of providing long-wavelength sensitivity and increasing the number of printing sheets by increasing hardness.

To judge the performance of a photoreceptor, (a) corona charging characteristics that represent the amount of charge given by corona discharge at a constant output, and (b) the amount of charge lost while holding the photoreceptor charged by corona discharge. Related dark decay characteristics, (c) charge voltage exposure decay characteristics that indicate the speed at which the amount of charge held in the dark disappears due to exposure, and (d) potential that remains without disappearing to zero after exposing the photoreceptor to light. Residual potential, etc. representing , are considered.

Residual potential in particular plays an important role in stabilizing the contrast and image quality of electrophotography and the properties of selenium photoreceptors. However, if selenium and tellurium are simply alloyed, the residual potential will be large, resulting in poor image quality such as background smearing.

For this reason, chlorine has conventionally been added.
However, when chlorine is added, the dark decay characteristics deteriorate. In addition, chlorine is usually added in the form of selenium tetrachloride, but it has a strong deliquescent property and is easily vaporized, causing many problems in handling.

Summary of the Invention The present inventor investigated the use of a selenium-tellurium alloy with a purity of over 99.999%, which is more pure than conventionally used alloys, and reduced the residual potential while maintaining good dark decay characteristics. As a result of conducting research on additives that can do this, it was discovered that the addition of oxygen is effective. More than 100ppm
By adding 1000 ppm or less of oxygen, the residual potential can be sufficiently reduced while maintaining good dark decay characteristics. Oxygenation does not present handling hazards as does chlorine.

Thus, the present invention provides: (1) an electrophotographic light-sensitive material characterized in that more than 100 ppm and less than 1000 ppm of oxygen is added to a selenium-tellurium alloy having a purity of more than 99.999%; (2) a purity of more than 99.999% an electrophotographic photoreceptor comprising a thin film photosensitive layer formed on a conductive substrate using an electrophotographic material in which oxygen is added to a selenium-tellurium alloy of 100 ppm to 1000 ppm; and (3) a laminated electrophotographic photoreceptor. In the body, a thin film photosensitive layer formed on a conductive substrate using an electrophotographic photosensitive material containing a selenium-tellurium alloy with a purity of more than 99.999% and oxygen added in an amount of more than 100 ppm and less than 1000 ppm is placed on top of a pure selenium or other photosensitive layer. Alternatively, an electrophotographic photoreceptor having one or more layers underneath is provided.

DETAILED DESCRIPTION OF THE INVENTION In preparing the selenium-tellurium alloy that is the base material in the photosensitive material of the present invention, the selenium-tellurium alloy has a higher purity than the conventionally used selenium and tellurium with a purity of 4 to 5N (99.99 to 99.999%). High purity selenium and tellurium of greater than 99.999%, typically 6N, is used. It is believed that if a raw material containing many impurities is used, the impurities will form traps, making it impossible for oxygen to sufficiently compensate for structural defects in the selenium-tellurium alloy itself.

In the present invention, more than 100 ppm and less than 1000 ppm of oxygen is added. By adding more than 100 ppm of oxygen, the residual potential is reduced to a sufficiently low level and the dark decay properties are also maintained well. 1000ppm
Even if oxygen is added in excess of this amount, the effect does not substantially change. Further, if more than 1000 ppm of oxygen is added, bumping is likely to occur during vapor deposition, causing defects in the deposited film, so from this point of view as well, it is desirable that the amount of oxygen be 1000 ppm or less.

Oxygen may be added in the form of SeO ₂ or by oxygen bubbling. In the case of oxygen addition, there are no problems in handling as in the case of chlorine addition.

An electrophotographic photoreceptor is obtained by vacuum-depositing the thus obtained electrophotographic photosensitive material, ie, a selenium-tellurium-oxygen alloy material as a vapor deposition source, onto a drum conductive substrate. As mentioned above, single-layer type and laminated type photoreceptors have been put into practical use. In the latter case, the photosensitive material of the present invention is used to form a photosensitive layer.

The conditions for vacuum evaporation are not particularly limited;
The conditions normally practiced are sufficient. Evaporation source temperature 250 to 350℃, substrate temperature 55 to 75℃, degree of vacuum 10 ^-5 to
It can be carried out by selecting appropriate conditions within the range of 10 ⁻⁶ Torr and evaporation time of 60 to 130 minutes. As the substrate, a metal such as aluminum or steel, metalized paper, or plastic is used.

The amount of tellurium in the selenium-tellurium alloy is generally 5 to 30% by weight. If it is less than 5%, the desired objectives of increasing long-wavelength sensitivity and printing durability cannot be achieved, while if it exceeds 30%, the selenium photosensitive characteristics will deteriorate beyond tolerance.

Regarding photoconductors for copying machines, photoconductors employing a layered structure called a functionally separated type have also been proposed. For example, in the case of a two-layer structure, the surface layer that receives direct light irradiation and is in contact with the paper surface is made of SE-Te material, which has excellent long-wavelength sensitivity and wear resistance, and the substrate side layer is made of pure selenium. . The present invention can be applied as one or more photosensitive layers of such a laminated electrophotographic photoreceptor.

Example A predetermined amount of high-purity selenium (purity 6N), tellurium (purity 6N), and selenium dioxide were sealed in a Pyrex ampoule with an outer diameter of 30 mm and a length of 220 mm.
After reacting in a rocking furnace at 550°C for 2 hours, it was taken out of the furnace and cooled in air. The ampoule was then crushed to remove the alloy. The tellurium concentration was 15 wt%, and the amount of oxygen added was varied from 1 to 1000 ppm.

The alloy produced in this way is heated by resistance heating.
Vacuum deposition was performed on a 55 mm x 55 mm mirror-finished aluminum substrate. The deposition conditions are as follows.

Evaporation source temperature: 300°C Substrate temperature: 70°C Vacuum degree: 2×10 ^-6 Torr Vapor deposition time: 90 minutes The thickness of the deposited film formed on the aluminum substrate under the above conditions was approximately 50 μm.

The electrophotographic properties of the alloy vapor-deposited film thus obtained were measured using an electrostatic testing device. The measurement conditions are as follows.

Corona discharge voltage 5kV Dark decay time 10 seconds Light irradiation time 30 seconds Light Illuminance 10 lux Static elimination illuminance, time 20000 lx, 2 seconds Repeat count 30 times The measurement results are shown in the drawing in relation to the amount of oxygen added to the alloy.

In Figure 1, the curve shows the initial surface potential;
The curve shows the surface potential (V ₁₀ ) in the dark state 10 seconds after charging. FIG. 2 shows the relationship between the residual potential and the amount of oxygen added. As can be seen from FIG. 2, the residual potential is sufficiently reduced in the range of oxygen addition of more than 100 ppm and less than 1000 ppm, and the dark decay characteristics at this time are also good as seen in FIG.

Effects of the Invention According to the present invention, a selenium-tellurium electrophotographic photoreceptor can be obtained which has a reduced residual potential while maintaining good dark decay characteristics.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the amount of oxygen added and the surface potential, and FIG. 2 is a graph showing the relationship between the amount of oxygen added and the residual potential.

Claims (1)

[Scope of Claims] 1. An electrophotographic light-sensitive material characterized in that more than 100 ppm and less than 1000 ppm of oxygen is added to a selenium-tellurium alloy having a purity of more than 99.999%. 2. An electrophotographic photoreceptor comprising a thin film photosensitive layer formed on a conductive substrate using an electrophotographic photosensitive material in which oxygen is added to a selenium-tellurium alloy having a purity of more than 99.999% and more than 100 ppm and less than 1000 ppm. 3 In a laminated electrophotographic photoreceptor, oxygen is added to a selenium-tellurium alloy with a purity of over 99.999%.
An electrophotographic photoreceptor comprising one or more thin film photosensitive layers formed on a conductive substrate using an electrophotographic photosensitive material containing more than 100 ppm and less than 1000 ppm on or below a pure selenium or other photosensitive layer.